Titanium beta s-alloy

ABSTRACT

An improved titanium beta alloy and method for the preparation thereof consisting of the following components in the percent by weight indicated: 10.0 - 12.0% molybdenum; 4.0 - 6.0% zirconium; 3.5 - 5.5% tin; 0.4 - 1.5% tantalum; 0.2 - 1.2% columbium, and the remainder titanium.

nitcd States Patent 1 Schuler et al.

[ 1 Oct. 23, 1973 TITANIUM BETA S-ALLOY [75] Inventors: Mary F. Schuler, Virginia Beach,

, Va.; Ernest P. Abrahamson,

Waltham, Mass.

[73] Assignee: The United States of America as represented by the Secretary of the Army, Washington, DC.

[22] Filed: Oct. 27, 1971 [21] Appl. No.: 190,455

[52] U.S. Cl 148/325, 75/175.S, l48/12.7 [51] Int. Cl C22c 15/00, C22f 1/18 [58] Fieldof Search 75/175.5, 11.5;

[56] References Cited UNITED STATES PATENTS 3,269,825 8/1966 Vordahl 75/175.5 X

Primary Examiner-Charles N. Lovell Attorney-Harry M. Saragovitz et al.

[57] ABSTRACT An improved titanium beta alloy and method for the preparation thereof consisting of the following compov nents in the percent by weight indicated: 10.0 12.0% molybdenum; 4.0 6.0% zirconium; 3.5 5.5% tin; 0.4 1.5% tantalum; 0.2 1.2% columbium, and the remainder titanium.

2 Claims, No Drawings TITANIUM BETA S-ALLOY The invention described herein may be manufactured, used, and licensed by or for the Government for governmental purposes without the payment to us of any royalty thereon.

This invention relates to a titanium beta alloy comprising an ultra fine grain composition thereby resulting in improved strength characteristics.

A titanium alloy known as Titanium Beta III is commercially available. The alloy comprises, e.g., the following components in the percent by weight indicated; 1 1.0% molybdenum; 6.0% zirconium; 4.5% tin and 78.5% titanium. In addition to the above components, the present titanium beta S-alloy comprises small amounts of transition metal solutes, i.e., tantalum andcolumbium. The present alloy hasbeen designated an S alloy in order to distinguish it over other alloys.

The inclusion of the transition metal solutes serves toraise the recrystallization temperature during fabrication, i.e., forging or rolling of the alloy at a temperature of about 1350 1400F. Raising the recrystallization temperature allows a higher temperature of deformation and hence greater. ease of deformation.. At'the same time, higher recrystallization temperatures inhibits grain growth which allows formation of a submicron grain size. For optimum properties, the fabricated alloy is subsequently heat treated at a temperature of about 900F for a period of about 8 hours in ambient air.

It is an object of this invention to provide and disclose an improved titanium beta alloy.

It is a further object of this invention to provide and disclose a titanium beta alloy having improved yield It is a further object of this invention to provide and 1 disclose a method for the production. of an improved titanium beta alloy.

An exemplary composition of the alloy was prepared utilizing about 1 lb. of a mixture consisting of the following components in the percent by weight indicated: 78.15% Ti; 11.0% M; 5.0% Zr; 4.5% Sn; 1.0% Ta and 5 0.35 Cb. A range of 10.0 12.0% M0; 4.0 -6.0% Zr;

3.5 5.5% Sn; 0.4 1.5% Ta; 0.2 1.2% Cb and the remainder Ti has been found operable. The mixture was placed into a water-cooled copper crucible and the crucible positioned into a conventional electric furnace equipped with tungsten electrodes for are melting. The

mixture was melted, cooled and subsequently remelted two more times in order to insure homogeneity. The resultant ingot had a grain size of about one millimeter to about one centimeter.

material is subsequently cooled'inambi'entair'to ro'om temperature.

Tensile specimens were machined from forged inch diameter bars. Certain of the bars were heated for a period of8 hours at a temperature of about 900F. The objective of the heat treatment is to effect or accelerate the precipitation and agglomeration of the constituents held'in supersaturated solid solution. This treatment is called ageing or age-hardening.

I Metallo g raphic examination of the microstructure of the fabricated alloy at a magnification of 1 500X has indicated that the grain size developed in the present alloy is in the range of 1 micron or less. This was confirmed by an electron transmission study which established a grain size of 0.9 microns.

' The tensile specimens, i.e., forged and age-hardened,

40- were subjected to mechanical tests to evaluate their mechanical properties. Composite results consisting of the average of about 10 individual evaluations of tensile specimens are set forth inTable 1 below.

TABLE 1 Yield strength Tensile Percent Percent Time Ksi (0.2 strength .elongareduction Hardness (hours) percent) Ksi tion in area -Rc 1 As forged 117.6 181.9 5.23 15.5 36.5 2 900F 8 258.4

Other objects and a fuller understanding of the in ven tion may be ascertained from the following description and claims.

Available data-in regards to the mechanical characteristics of commercially available titanium beta 111 is set forth in Table 11 below I The present titanium alloy exhibits significant improvement in yield and tensile strength over the prior I art titanium beta llI alloy. The present alloy in the as forged condition exhibits improvements in the range of about 60 percent yeild strength and about 65 per-v A prior art heat treatedtitaniurn beta Ill tt ile specimen was examined for grain size and tested for hardness. The grain size was in the range of 2-3 microns. This compares with a grain size of less than 1 micron for the present alloy. In addition, the hardness of the prior art alloy was Re 35 compared with a hardness of Re 48 for the present alloy.

Presently, considerable interest is focused on the development of high strength-to-density ratio titanium alloy because of military requirements for aircraft, armor and structural applications. However, the present titanium alloy could be advantageously utilized in any structure requiring a material having a high strength-to-density ratio.

Although we have described our invention with a certain of particularity it is understood that the present disclosure has been made only by way of example and that numerous changes may be made in the preparation and fabrication of the present alloy without departing from the spirit and scope of the invention.

Having described our invention, we claim:

1. A wrought age-hardened titanium beta S-alloy product having a fine grain size in the range of 1 micron or less and consisting of the following components in the percent by weight indicated:

M0 10.0-12.0 Zr 4.0-6.0 Sn 3.5-5.5 Ta 0.4-1.5 Cb 0.2- l .2

and the remainder titanium, said product having been reduced during fabrication until a minimum breakdown of material of at least 4 to l is achieved.

2. A titanium beta S-alloy product in accordance with claim 1 consisting essentially of the following components in the percent by weight indicated:

Mo ll.0 Zr 5.0 Sn 4.5 Ta [.0 Cb 0.35 Ti 78.l5 

2. A titanium beta S-alloy Product in accordance with claim 1 consisting essentially of the following components in the percent by weight indicated: Mo11.0 Zr5.0 Sn4.5 Ta1.0 Cb0.35 Ti78.15 